The author's iPhone 16 Pro Max produces incorrect output when running MLX LLMs, while an iPhone 15 Pro and a MacBook Pro run the same code perfectly. The issue is suspected to be a hardware defect in the Neural Engine or another ML-related system. The author debugged the issue by comparing tensor outputs on different devices and found that the iPhone 16 Pro Max's output was orders of magnitude off. The problem was resolved when the author upgraded to an iPhone 17 Pro Max.